CN114362237A - Multi-mode flexible direct-current power grid cooperative control method - Google Patents

Multi-mode flexible direct-current power grid cooperative control method Download PDF

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CN114362237A
CN114362237A CN202111363962.XA CN202111363962A CN114362237A CN 114362237 A CN114362237 A CN 114362237A CN 202111363962 A CN202111363962 A CN 202111363962A CN 114362237 A CN114362237 A CN 114362237A
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direct current
grid
power
voltage
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刘永庆
龙日尚
冯世运
赵元磊
高玉瑄
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State Grid Corp of China SGCC
State Grid Tianjin Electric Power Co Ltd
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State Grid Tianjin Electric Power Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
    • Y02B70/3225—Demand response systems, e.g. load shedding, peak shaving
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
    • Y04S20/20—End-user application control systems
    • Y04S20/222—Demand response systems, e.g. load shedding, peak shaving

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Abstract

The invention relates to a multi-mode flexible direct-current power grid cooperative control method, which comprises the following steps: step 1, establishing a multi-terminal flexible direct current grid system model comprising distributed energy, energy storage, a grid-connected converter and a load unit according to the actual operation condition of a wind-solar-energy storage direct current grid; step 2, based on the multi-terminal flexible direct current grid system model established in the step 1, generating an instruction value S according to the change interval of direct current voltage, and switching the operation mode of each converter station according to the instruction value S; and 3, introducing hysteresis control in the process that each converter station in the step 2 switches the operation mode according to the instruction value S. The invention can ensure the power balance, the voltage stability and the safe operation of the flexible direct current power grid under the working conditions of larger fluctuation of external conditions, more generated energy or overhigh load demand and the like.

Description

Multi-mode flexible direct-current power grid cooperative control method
Technical Field
The invention belongs to the technical field of flexible direct current control, and relates to a flexible direct current power grid cooperative control method, in particular to a multi-mode flexible direct current power grid cooperative control method.
Background
With the continuous improvement of power consumption requirements and power quality requirements and the long-term development and wide application of new energy, new materials and power electronic technologies, the traditional alternating-current power distribution network faces a series of problems such as distributed energy access, load diversity, complex primary system structure, load scheduling and tide balance coordination control complexity and the like.
The flexible direct current transmission adopted by the flexible direct current power grid adopts a Voltage Source Converter (VSC) based on a full-control device, and the flexible direct current power grid has the advantages of current self-turn-off capability, capability of supplying power to a passive network and the like, so that people pay attention to the flexible direct current transmission and the flexible direct current transmission is developed rapidly. Compared with an alternating current power grid, the flexible direct current power grid has more excellent performance in the aspects of improving electric energy transmission capacity, increasing system controllability, improving power supply quality and the like, can better coordinate contradictions between distributed energy resources and the power grid, and fully explores benefits and values of the distributed energy resources.
The flexible direct-current power grid has the control problems of small system inertia, more component elements, large voltage fluctuation, frequent power disturbance, more controllable ends, complex power grid topology and operation mode and the like. The current control mode of the flexible direct current network is simpler, and master-slave control, droop control and deviation control are basically adopted. These several methods have drawbacks and deficiencies. The deviation control design is complex, the voltage control effect is poor in a steady-state operation state, and the voltage index is poor when the load fluctuation is frequent. In the case of droop control, a large static error occurs in the voltage. Master-slave control has a high requirement for communication. In addition, the existing control mode causes frequent startup of the controller when the power fluctuation is near a critical value, and the service life of the components is influenced.
Therefore, how to develop a multi-mode flexible dc power grid cooperative control method can solve the control problems of small system inertia, many component elements, large voltage fluctuation, frequent power disturbance, many controllable ends, complex power grid topology and operation manner, and the like, and is a problem to be solved by those skilled in the art.
Through searching, no prior art document which is the same as or similar to the prior art document is found.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a multi-mode flexible direct-current power grid cooperative control method which can ensure the power balance, the voltage stability and the safe operation of a flexible direct-current power grid under the working conditions of large fluctuation of external conditions, more generated energy or overhigh load demand and the like.
The invention solves the practical problem by adopting the following technical scheme:
a multi-mode flexible direct current power grid cooperative control method comprises the following steps:
step 1, establishing a multi-terminal flexible direct current grid system model comprising distributed energy, energy storage, a grid-connected converter and a load unit according to the actual operation condition of a wind-solar-energy storage direct current grid;
step 2, based on the multi-terminal flexible direct current grid system model established in the step 1, generating an instruction value S according to the change interval of direct current voltage, and switching the operation mode of each converter station according to the instruction value S;
and 3, introducing hysteresis control in the process that each converter station in the step 2 switches the operation mode according to the instruction value S.
Moreover, the multi-end flexible direct current grid system model in the step 1 adopts a topological structure with two ends for power distribution, and comprises a distributed power generation unit, an energy storage unit, a load unit and two grid-connected converters; the distributed power generation unit adopts a photovoltaic cell, is merged into a direct current power grid through PV-DC, is used for absorbing light energy and provides energy for providing; the energy storage unit stores energy by adopting a storage battery, and is merged into a direct current power grid through a DC/DC converter Bi-DC for dynamically adjusting the power balance of the system; the load unit is merged into a direct current network through a converter L-VSC and is used for absorbing power, participating in system power distribution and switching load when necessary; two ends of the direct current power grid are respectively merged into the alternating current power grid through two grid-connected converters G-VSC, and the grid-connected converters are used for providing power support and maintaining voltage stability.
Moreover, the operation mode of step 2 includes: a power balance state, a power excess state, a power reduction state, and a power deficit state.
In step 2, a method for generating the command value S according to the variation interval of the dc voltage and switching the operation mode of each converter station according to the command value S is shown in the following table:
Figure BDA0003359931190000031
the specific method of step 3 is: when the direct current voltage changes, two different thresholds are set near the critical value, and when S is from 1 to 4 and from 4 to 1, the direct current voltage threshold for triggering the switching of the command value S is slightly different. This ensures that the command value S does not change frequently when the dc voltage fluctuates around the critical value.
The invention has the advantages and beneficial effects that:
1. the invention relies on the wind-solar-energy storage direct-current power grid of the national grid Tianjin North-Chen green energy smart park, establishes a multi-terminal flexible power grid model of units such as distributed energy, energy storage, grid-connected current converter, load and the like, and forms an 'operation mode under five states' by optimizing direct-current voltage indexes, dispersing autonomous control effects and adding hysteresis control on the basis of direct-current voltage deviation control and direct-current voltage droop control: a power balance state, a power excess state, a power reduction state, a power deficit state. Therefore, the control problems of small system inertia, more constituent elements, large voltage fluctuation, frequent power disturbance, more controllable ends, complex power grid topology and operation mode and the like are effectively solved, and the voltage stability and the power balance of the system are guaranteed.
2. The multi-mode flexible direct-current power grid cooperative control method is beneficial to solving a plurality of control problems of a wind-light storage flexible direct-current power grid system formed by distributed energy such as wind energy and light energy (solar energy) under working conditions of large fluctuation of external conditions, more generated energy or overhigh load demand and the like, achieves the aims of stable system voltage and power balance, ensures the power balance, stable voltage and safe operation of the flexible direct-current power grid, saves the operation cost of enterprises, improves the social benefit, and provides reliable guarantee for the economic and social development of power supply areas.
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FIG. 1 is a diagram of a multi-terminal flexible DC power grid system model of the present invention;
FIG. 2 is a schematic diagram of a control concept with a command value S according to the present invention;
FIG. 3 is a graph of the voltage segment control characteristic of the present invention;
FIG. 4 is a diagram illustrating the relationship between DC voltage threshold and control mode switching commands according to the present invention.
Detailed Description
The embodiments of the invention will be described in further detail below with reference to the accompanying drawings:
a multi-mode flexible direct current power grid cooperative control method comprises the following steps:
step 1, establishing a multi-terminal flexible direct current grid system model comprising distributed energy, energy storage, a grid-connected converter and a load unit according to the actual operation condition of a wind-solar-energy storage direct current grid;
the multi-end flexible direct current grid system model in the step 1 adopts a topological structure with two ends for power distribution, and comprises a distributed power generation unit, an energy storage unit, a load unit and two grid-connected converters; the distributed power generation unit adopts a photovoltaic cell, is merged into a direct current power grid through PV-DC, is used for absorbing light energy and provides energy for providing; the energy storage unit stores energy by adopting a storage battery, and is merged into a direct current power grid through a DC/DC converter Bi-DC for dynamically adjusting the power balance of the system; the load unit is merged into a direct current network through a converter L-VSC and is used for absorbing power, participating in system power distribution and switching load when necessary; two ends of the direct current power grid are respectively merged into the alternating current power grid through two grid-connected converters G-VSC, and the grid-connected converters are used for providing power support and maintaining voltage stability.
In this embodiment, the topology structure of the dc power grid mainly includes three types, namely radial type, ring network and two-end power distribution, and the present invention adopts the topology structure of two-end power distribution according to the actual operation condition of the wind, light and storage dc power grid in the national grid tianjin north-hour green energy smart park, and sets the voltage to 10kV, and the structure of the topology structure is shown in fig. 1 (model diagram of multi-end flexible dc power grid system), and the topology structure includes the following components:
1) distributed power generation unit: photovoltaic cells are adopted and are incorporated into a direct current power grid through PV-DC. When the photovoltaic module normally operates, the photovoltaic module works in a Maximum Power Point Tracking (MPPT) mode to capture solar energy as much as possible, but when the voltage rises more, the photovoltaic module needs to be operated by reducing power.
2) An energy storage unit: the energy storage Battery (BES) is adopted and is merged into a direct current power grid through a DC/DC converter Bi-DC. When the direct current power grid normally and stably operates, the power of the storage battery is zero. When the voltage fluctuation is large, the BES unit participates in the regulation of the direct current voltage.
3) A load cell: the AC load is merged into the DC network through a converter L-VSC.
4) Grid-connected converter: the direct current power grid is merged into the alternating current power grid through a converter G-VSC. The converter participates in the DC voltage control during normal operation. When the system power changes greatly, the power limit is reached and the control is changed into constant power control.
Step 2, based on the multi-terminal flexible direct current grid system model established in the step 1, generating an instruction value S according to the change interval of direct current voltage, and switching the operation mode of each converter station according to the instruction value S;
the operation mode of the step 2 comprises the following steps: a power balance state, a power excess state, a power reduction state, and a power deficit state.
The method for generating the command value S according to the change interval of the dc voltage in step 2 and switching the operation mode of each converter station according to the command value S is shown in the following table:
Figure BDA0003359931190000061
in this embodiment, in order to cope with different operation states of the system, the converter stations need to cooperate with each other, and the control concept is as shown in fig. 2. Each converter station detects the values before and after the change of the direct current voltage, and obtains a command value S according to the direct current voltage value in the table 1, so that the command value becomes a medium for linking the direct current voltage with the bottom layer controller; and each converter station switches the operation mode according to the instruction value and the control strategy table (table 1).
Meanwhile, the command value S for controlling the mode switching is also used in the upper control, and becomes the amount of information linking the lower control and the upper control.
In a direct current power grid, the direct current voltage of a system is the key of stable operation of the system.
The invention provides a voltage cooperative control strategy of sectional control, and different direct current voltage operation ranges correspond to respective intervals. The control mode of the converter is reasonably set in the control interval to keep the direct current voltage of the system stable, and at least one end converter in each interval controls the direct current voltage to maintain the internal power balance of the system.
After obtaining the command value S according to the direct-current voltage variation, each converter station operates a corresponding controller, and the implementation method of the control strategy is as shown in the table 1:
TABLE 1 control policy table for each terminal
Figure BDA0003359931190000071
Each end in the direct current power grid executes the policy table by measuring the value of the direct current voltage, and participates in the overall cooperative control of the system. The control operation of each converter station of the control strategy is independent and quick in response, the control strategy can be adjusted in real time according to the change of system operation, communication is not needed, and the characteristics of decentralized self-discipline and multipoint coordination are achieved.
Meanwhile, the instruction value S is introduced into the control strategy, so that the control strategy can not only play a role in a bottom-layer decentralized and autonomous control strategy table, but also be difficult to control the stability of the direct-current voltage by simply adopting the control strategy table when faults such as short circuit, disconnection and the like occur in a system or the power fluctuates greatly, and a corresponding fault module needs to be added into an upper-layer controller at the moment. The function of the method is to detect the system fault condition or large power fluctuation, generate a corresponding instruction value S through a certain algorithm or manual operation, and send the instruction value S to each converter station, so that each converter station forcibly switches a control mode or modifies a parameter value, thereby ensuring the direct-current voltage stability of the system under the transient condition.
The operation conditions of all intervals of the direct-current voltage cooperative control strategy are explained based on a converter station P-Udc (P is converter direct-current power, Udc is converter direct-current voltage) curve:
fig. 3 is a voltage section control characteristic diagram of the DC power grid proposed by the present strategy, which is respectively the control characteristics of G-VSC1, G-VSC2, Bi-DC, PV-DC, and L-VSC in different control intervals, and black dots in the diagram indicate that each end works in the optimal state, at which time the DC voltage Udc is 10 kV. P1, P2, Pev, Ppv and PL denote the power of G-VSC1, G-VSC2, Bi-DC, PV-DC and L-VSC, respectively. The power being positive indicates that the respective converter station is inputting power to the dc grid.
According to the advantages and disadvantages of master-slave control, droop control and deviation control, making up for the disadvantages, integrating the advantages of each control mode, making up for the disadvantages, forming a control strategy table which comprises 'operation modes under five states': a power balance state, a power excess state, a power reduction state, a power deficit state.
The actual working conditions corresponding to the five operation modes and the switching principle thereof are described in detail below. The control problems of small system inertia, more constituent elements, large voltage fluctuation, frequent power disturbance, more controllable ends, complex power grid topology and operation modes and the like in different operation environments are effectively solved, and the voltage stability and the power balance of the system are guaranteed.
The following describes the control conditions of each section and the control mode of the inverter at each end:
mode 1 (power balance): the dc voltage was varied in a range of 9.8 to 10.2kV, and the generation command value S was 1. During this interval, the system is in steady state. The photovoltaic unit carries out maximum energy tracking, and the photovoltaic unit emits electric energy as much as possible, so that the maximum utilization rate of the distributed energy is ensured. The storage battery keeps zero power after charging in order to prevent the service life of the storage battery from being damaged by frequent actions.
The load in the direct current power grid changes frequently, the power fluctuates all the time, and the droop control can monitor the power change of the system in real time, adjust the direct current power of each end and keep the direct current voltage stable. Therefore, in steady state, the G-VSC1 and the G-VSC2 employ droop control. In order to guarantee the power consumption requirement of the load, the alternating current load is controlled by constant alternating current voltage.
The range of the dc voltage in the mode 2 (power excess) is 10.2 to 10.5kV, the generation command value S is 2, the range of the dc voltage variation in the mode 4 (power reduction) is 9.5 to 9.8kV, and the generation command value S is 4. In the interval, the direct current voltage is not changed greatly, and in order to utilize new energy to the maximum extent, the photovoltaic still generates the maximum electric energy.
Wherein the G-VSC2, due to its converter capacity limitations and system control requirements, reaches maximum capacity, turning into power limited dc voltage deviation control. The G-VSC1 has larger capacity, and still keeps the direct-current voltage droop control participating in voltage regulation.
Due to the increase of the deviation amount of the direct-current voltage, the direct-current voltage is controlled by the G-VSC1 and the G-VSC2, and the operation requirement of a direct-current power grid cannot be met. The battery has sufficient energy margin and sufficient capacity to release energy. When the mode 4 power is reduced, the battery is discharged to participate in the dc voltage control according to the droop control characteristic. Mode 2 is power surplus and does not require energy storage discharge.
At the moment, the direct current voltage is still kept in a reasonable range, the load supply can be normally ensured, and the load still keeps constant alternating current voltage control.
In mode 3 (power excess), the range of the dc voltage is greater than 10.5kV, and the generation command value S is 3. In the interval, the system has power excess due to reasons such as excessive power generation or less load, and at the moment, the stored energy cannot absorb all the residual power and keeps zero-power operation, so that the direct-current voltage is increased.
At this time, both grid-connected converters reach the power limit thereof, and the control is converted into direct-current voltage deviation control. The grid-connected converter and the energy storage switching control mode can not control the direct-current voltage within a limited range, a photovoltaic power reduction measure is required to be adopted, the control is changed into constant direct-current voltage control, the direct-current voltage is stabilized at 10.5kV, and the stable operation of the system is ensured. At the moment, the system has excess power, and needs to be loaded completely, so that the electric energy is absorbed maximally.
In mode 5 (power shortage), the range of the dc voltage is less than 9.5kV, and the generation command value S is 5. In the interval, the system needs overlarge power due to load, even if the photovoltaic power generation is carried out by the maximum power, all electric energy is released by stored energy, and the deviation control of converting the maximum power of the grid-connected converter into the direct current voltage cannot be met, so that the system is in power shortage, and the direct current voltage of the bus rises.
At this time, the direct current voltage is too low, and it has become difficult to continue to stabilize the direct current voltage by other converter stations in a basic control mode, so as to prevent the direct current voltage from collapsing, the load is cut off, and the unimportant load and the important load are cut off in sequence according to the priority of the load until the direct current voltage returns to the stabilization interval.
And 3, introducing hysteresis control in the process that each converter station in the step 2 switches the operation mode according to the instruction value S.
The specific method of step 3 is: when the direct current voltage changes, two different threshold values are set near the critical value, and when S is from 1 to 4 and from 4 to 1, the trigger instruction value S switches the direct current voltage threshold value slightly differently. This ensures that the command value S does not change frequently when the dc voltage fluctuates around the critical value.
Finally, in the present embodiment, in order to prevent the converter station from frequently switching the control mode near the dc voltage threshold value, and thereby protect the components, a hysteresis control is added to the controller.
Due to frequent power disturbance of the direct-current power distribution network, the direct-current voltage is easy to change. In order to reduce frequent switching of modes, a command value S is set, assignment is carried out according to change of direct-current voltage, and hysteresis control is introduced.
The relationship between the dc voltage threshold and the command for controlling the mode switching is shown in fig. 4. FIG. 4(a) shows that when the DC voltage is decreased from 10kV, S is switched from 1 to 4 after the DC voltage is decreased to 9.8kV, and S is switched from 4 to 5 after the DC voltage is further decreased to 9.5 kV; correspondingly, as shown in fig. 4(b), when the dc voltage starts to increase from 9kV, S is switched from 5 to 4 after increasing to 9.55kV, and S is switched from 4 to 1 after continuing to increase to 9.85 kV.
The main innovation of the invention is that:
(1) and optimizing the indexes of the direct current voltage. The invention optimizes the control effect of droop control and deviation control under transient state and steady state, and better solves the problems of large static voltage error in the transient state of droop control and poor voltage index in the steady state of deviation control through the reduction of direct current voltage variance value and overshoot (table 2 direct current voltage index data comparison table).
TABLE 2 DC VOLTAGE INDICATOR DATA COMPARATIVE TABLE
Deviation of Slope of Strategy of the invention
Variance (variance) 0.00038 0.00026 0.00010
Overshoot 0.00386 0.00226 0.00164
(2) And (4) dispersing the self-discipline control effect. The problem that master-slave control needs communication coordination is solved, each unit does not need an additional communication mode, and when the system has working conditions of distributed energy power fluctuation, converter station switching, load change and the like, the control mode can be independently adjusted according to the direct-current voltage change, so that the overall power of the system is balanced, and the decentralized and autonomous control effect is achieved. The control scheme of the flexible direct-current power grid after the distributed energy grid connection is provided, and the control problems that the direct-current power grid system is small in inertia, multiple in component elements, large in voltage fluctuation, frequent in power disturbance, multiple in controllable ends, complex in power grid topology and operation mode and the like are solved.
(3) Hysteresis control is added. Because the power of the direct-current power distribution network fluctuates frequently, the direct-current voltage is easy to change continuously. In order to prevent the converter station from frequently switching the control mode near the critical value of the direct-current voltage, hysteresis control is added into the controller, and a plurality of threshold values are added near the critical value to assign a command value S, so that the controller is prevented from being frequently started, and the service life of components is effectively prolonged.
It should be emphasized that the examples described herein are illustrative and not restrictive, and thus the present invention includes, but is not limited to, those examples described in this detailed description, as well as other embodiments that can be derived from the teachings of the present invention by those skilled in the art and that are within the scope of the present invention.

Claims (5)

1. A multi-mode flexible direct current power grid cooperative control method is characterized by comprising the following steps: the method comprises the following steps:
step 1, establishing a multi-terminal flexible direct current grid system model comprising distributed energy, energy storage, a grid-connected converter and a load unit according to the actual operation condition of a wind-solar-energy storage direct current grid;
step 2, based on the multi-terminal flexible direct current grid system model established in the step 1, generating an instruction value S according to the change interval of direct current voltage, and switching the operation mode of each converter station according to the instruction value S;
and 3, introducing hysteresis control in the process that each converter station in the step 2 switches the operation mode according to the instruction value S.
2. The multi-mode flexible direct current power grid cooperative control method according to claim 1, characterized in that: the multi-end flexible direct current grid system model in the step 1 adopts a topological structure with two ends for power distribution, and comprises a distributed power generation unit, an energy storage unit, a load unit and two grid-connected converters; the distributed power generation unit adopts a photovoltaic cell, is merged into a direct current power grid through PV-DC, is used for absorbing light energy and provides energy for providing; the energy storage unit stores energy by adopting a storage battery, and is merged into a direct current power grid through a DC/DC converter Bi-DC for dynamically adjusting the power balance of the system; the load unit is merged into a direct current network through a converter L-VSC and is used for absorbing power, participating in system power distribution and switching load when necessary; two ends of the direct current power grid are respectively merged into the alternating current power grid through two grid-connected converters G-VSC, and the grid-connected converters are used for providing power support and maintaining voltage stability.
3. The multi-mode flexible direct current power grid cooperative control method according to claim 1, characterized in that: the operation mode of the step 2 comprises the following steps: a power balance state, a power excess state, a power reduction state, and a power deficit state.
4. The multi-mode flexible direct current power grid cooperative control method according to claim 1, characterized in that: the method for generating the command value S according to the change interval of the dc voltage in step 2 and switching the operation mode of each converter station according to the command value S is shown in the following table:
Figure FDA0003359931180000021
5. the multi-mode flexible direct current power grid cooperative control method according to claim 1, characterized in that: the specific method of the step 3 comprises the following steps: when the direct current voltage changes, two different thresholds are set near the critical value, and when S is from 1 to 4 and from 4 to 1, the direct current voltage threshold for triggering the switching of the instruction value S is different.
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Publication number Priority date Publication date Assignee Title
CN117878869A (en) * 2024-03-11 2024-04-12 绵阳正能新能源技术有限公司 DC voltage stabilization control method of DC micro-grid system
CN117878869B (en) * 2024-03-11 2024-05-28 绵阳正能新能源技术有限公司 DC voltage stabilization control method of DC micro-grid system

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